As is well known in the art, motor vehicle wheels are mounted to hubs fast for rotation with an axle journal or an axle shaft, according to the specific function of the wheel.
It is known to use a cover, generally made of sheet metal, to close the through bore at the center of the hub in order to prevent external agents from reaching and contaminating the axle and the other hub components, for example the hub bearing.
In conventional solutions, the cover is forcefully fitted inside a centering sleeve portion or spigot axially projecting from the hub. The wheel forms a radially inner annular rim by which it is then mounted and centered onto said spigot.
This solution, although widely applied, has some drawbacks. Particularly, the contacting surfaces between the hub and the wheel and between the hub and a radial flange of an optional brake member (disc or drum) are likely to suffer from corrosion caused by external contaminants. Corrosion is also caused by the differential of galvanic potential between the different metallic materials which these components are made of. The intensity and entity of the corrosion is proportional to such difference of galvanic potential. This problem is particularly felt with light metal alloy wheels.
To avoid this inconvenience, said components have to be made out of special materials, thereby increasing manufacturing costs. Alternatively, the hub spigot must undergo an anti-corrosion processing, which is extremely difficult to attain with satisfactory results.